Harry, so sorry, I'm short on time right now, and really, there is SO MUCH information about cockroaches online that it doesn't make sense for me to try to summarize it for you.
Best to research which roaches species are common in your area. There are many, many tips available for reducing (you'll never eradicate) the populations and for keeping them out of your house, from physical barriers & adjustments to chemical warfare. I find that sticky traps near the door work just fine if you don't have an infestation.
Good luck!
